Abstract: In this letter we revisit the idea of reionization feedback on dwarf galaxy
formation. We show that primordial minihalos with v_cir<20 km/s stop accreting
gas after reionization, as it is usually assumed, but in virtue of their
increasing concentration and the decreasing temperature of the intergalactic
medium as redshift decreases below z=3, they have a late phase of gas accretion
and possibly star formation. We expect that pre-reionization fossils that
evolved on the outskirts of the Milky Way or in isolation show a bimodal star
formation history with 12 Gyr old and <10 Gyr old population of stars. Leo T
fits with this scenario. Another prediction of the model is the possible
existence of a population of gas rich minihalos that never formed stars. More
work is needed to understand whether a subset of compact high-velocity clouds
can be identified as such objects or whether an undiscovered population exists
in the voids between galaxies.